Dataset Information

Increased chemical weathering during the deglacial to mid-Holocene summer monsoon intensification.

ABSTRACT: Chemical weathering and the ensuing atmospheric carbon dioxide consumption has long been considered to work on geological time periods until recently when some modelling and natural records have shown that the weathering-related CO₂ consumption can change at century to glacial-interglacial time scale. Last glacial to interglacial transition period is a best test case to understand the interplay between Pco₂-temperature-chemical weathering when a pulse of rapid chemical weathering was initiated. Here we show, from a high resolution 54 ka record from the Andaman Sea in the northern Indian Ocean, that the chemical weathering responds to deglacial to mid-Holocene summer monsoon intensification in the Myanmar watersheds. The multi-proxy data (Al/K, CIA, Rb/Sr, ⁸⁷Sr/⁸⁶Sr for degree of weathering and ¹⁴³Nd/¹⁴⁴Nd for provenance) reveal an increase in silicate weathering with initiation of interglacial warm climate at ~17.7 ka followed by a major change at 15.5 ka. Inferred changes in chemical weathering have varied in tandem with the regional monsoonal proxies (δ¹⁸O_sw-salinity changes of Northern Indian Ocean, effective Asian moisture content and δ¹⁸O records of Chinese caves) and are synchronous with changes in summer insolation at 30°N and δ¹⁸O of GISP2 implying that chemical weathering was not a later amplifier but worked in tandem with global climate change.

SUBMITTER: Miriyala P

PROVIDER: S-EPMC5355878 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Increased chemical weathering during the deglacial to mid-Holocene summer monsoon intensification.

Miriyala Pavan P Sukumaran N P NP Nath B Nagender BN Ramamurty P B PB Sijinkumar A V AV Vijayagopal B B Ramaswamy V V Sebastian Tyson T

Scientific reports 20170317

Chemical weathering and the ensuing atmospheric carbon dioxide consumption has long been considered to work on geological time periods until recently when some modelling and natural records have shown that the weathering-related CO<sub>2</sub> consumption can change at century to glacial-interglacial time scale. Last glacial to interglacial transition period is a best test case to understand the interplay between Pco<sub>2</sub>-temperature-chemical weathering when a pulse of rapid chemical weat ...[more]

PMID: 28303943

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Project description:Tropical climate is rapidly changing, but the effects of these changes on the geosphere are unknown, despite a likelihood of climatically-induced changes on weathering and erosion. The lack of long, continuous paleo-records prevents an examination of terrestrial responses to climate change with sufficient detail to answer questions about how systems behaved in the past and may alter in the future. We use high-resolution records of pollen, clay mineralogy, and particle size from a drill core from Lake Malawi, southeast Africa, to examine atmosphere-biosphere-geosphere interactions during the last deglaciation (∼ 18-9 ka), a period of dramatic temperature and hydrologic changes. The results demonstrate that climatic controls on Lake Malawi vegetation are critically important to weathering processes and erosion patterns during the deglaciation. At 18 ka, afromontane forests dominated but were progressively replaced by tropical seasonal forest, as summer rainfall increased. Despite indication of decreased rainfall, drought-intolerant forest persisted through the Younger Dryas (YD) resulting from a shorter dry season. Following the YD, an intensified summer monsoon and increased rainfall seasonality were coeval with forest decline and expansion of drought-tolerant miombo woodland. Clay minerals closely track the vegetation record, with high ratios of kaolinite to smectite (K/S) indicating heavy leaching when forest predominates, despite variable rainfall. In the early Holocene, when rainfall and temperature increased (effective moisture remained low), open woodlands expansion resulted in decreased K/S, suggesting a reduction in chemical weathering intensity. Terrigenous sediment mass accumulation rates also increased, suggesting critical linkages among open vegetation and erosion during intervals of enhanced summer rainfall. This study shows a strong, direct influence of vegetation composition on weathering intensity in the tropics. As climate change will likely impact this interplay between the biosphere and geosphere, tropical landscape change could lead to deleterious effects on soil and water quality in regions with little infrastructure for mitigation.

Dataset Information

Increased chemical weathering during the deglacial to mid-Holocene summer monsoon intensification.

Publications

Increased chemical weathering during the deglacial to mid-Holocene summer monsoon intensification.

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